Andrew Stroehlein, the European media director of Human Rights Watch, responded by saying that the NGO’s “detailed investigation into three cases found that national police and Civil Guard used excessive force”.

“The police may well have had the law on their side to enforce a court order but it didn’t give them the right to use violence against peaceful protesters,” said Kartik Raj, Western Europe researcher at Human Rights Watch.

Media outlets around the world showed scenes in which voters or volunteers running polling stations were beaten with truncheons, had their hair pulled or were otherwise manhandled as Spanish security forces attempted to enforce a ban on the referendum, which was ruled unconstitutional by Spain’s courts.

A report on Catalonia’s referendum by independent election observers from The Hague Centre for Strategic Studies condemned police violence it said had caused injuries to “hundreds of voters” on polling day.

“The use of force displayed by the Spanish police has no place in established democracies,” the report said.

Catalonia’s health department has since released a breakdown of the 991 patients it says required treatment on October 1 as a result of the scenes of confrontation between the police and citizens at polling stations.

According to the data, the biggest reasons for treatment were contusions and multiple contusions, together accounting for 818 patients. Fifty people were reported to have suffered wounds and gashes, with another 30 listed as having suffered a head trauma or concussion.

Most of those affected were dealt with by mobile ambulance units or in health centres, while 38 needed hospital treatment.

Among those hospitalised was a 38-year-old man treated for an eye injury believed to have been caused by rubber bullets, which were projectiles used by Spain’s national police force in Barcelona.

Catalonia’s government claimed that 90 per cent of 2.3 million people who voted had said yes to independence, which represents 38 per cent of the electorate.

Catalan President Carles Puigdemont claimed that the result gave the region a mandate to declare independence. Madrid responded on Saturday by announcing the imposition of direct rule over Catalonia.

Mr Puigdemont has said he will ask Catalonia’s parliament to debate and act against this “attempt to liquidate our self-government” in the coming days, prompting speculation that he was preparing to put a declaration of independence to a vote before calling regional elections.

However, the chief spokesman of Catalonia’s government said the calling of a snap election was “not on the table”.

Jordi Turull, speaking on Catalonia’s RAC1 radio station Sunday, said he did not rule out a unilateral declaration of independence. “What Catalonia is will be decided by the parliament legitimately elected by the citizens.”